This image provided by National Oceanic and Atmospheric Administration's (NOAA) National Weather Service Weather Prediction Center shows an early computer model forecasting the chances of a windy, strong sleet-snow storm hitting the East Coast this weekend, Jan. 22-23, 2016. Meteorologists say tens of millions of Americans from Washington to Boston and the Ohio Valley could be walloped by an end-of-the-week snowstorm. (National Oceanic and Atmospheric Administration via AP)

WASHINGTON (AP) — Drivers in the Washington area spent hours in icy gridlock ahead of heavy snowfall that’s predicted to arrive by the weekend from Appalachia to Philadelphia and maybe farther north.

On Thursday morning, Virginia Gov. Terry McAuliffe issued a state of emergency and said people should “take the threat of this storm seriously.” He warned of travel disruptions and power outages. McAuliffe said crews are treating roads before the weekend storm hits, but state transportation officials urged drivers to stay off roads until the storm passes.

Quentin Norman, a manager at a gas station and convenience store in Capitol Heights, Maryland, just outside Washington, said his commute home Wednesday took an hour instead of the usual 15 minutes. The traffic and storm “kind of took us by surprise,” he said.

“Everybody was talking about the weekend,” he said, and assumed Wednesday’s weather would just breeze through.

By morning rush hour, treated roads were mostly clear. But some elevated roads, ramps and side streets were icy with drivers inching along.

In Maryland, crews got stuck in lengthy backups Wednesday night, slowing their progress, state Department of Transportation spokesman Charlie Gischlar said. Major delays continued through the night on the Capital Beltway in Prince George’s County, but crews were making progress Thursday morning, he said.

In northern Virginia, minor accidents built to gridlock and ramp closures continued through the night, Virginia Department of Transportation spokeswoman Jennifer McCord said. She described “a long night for a lot of people trying to get home.” State police responded to 767 crashes over a 24-hour period ending early Thursday, and two troopers were involved in accidents, spokeswoman Corinne Geller said.

With more winter weather approaching, people throughout the region readied themselves for blocked roads, power outages and canceled flights.

The National Weather Service said in a statement Wednesday that 12 to 16 inches of snow could come down between Friday night and Sunday morning around the Interstate 95 corridor. As much as a foot of snow is possible for Philadelphia’s northern suburbs.

Mitchell Gaines of the National Weather Service in Mount Holly, New Jersey, said people should be prepared for strong winds, heavy, wet snow and power outages.

In the District of Columbia, Mayor Muriel Bowser requested Humvees from the National Guard to reach isolated people and places if necessary.

“If this is a blizzard and we have sustained winds and people lose power, that would be my biggest concern,” Bowser said at a news conference. “We can move the snow. We will move the snow.”

In the areas where blizzard conditions are possible, the weather service warns that travel will be limited or impossible. The strongest winds and potentially life-threatening conditions are expected Friday night through Saturday night.

On Wednesday, the weather service issued blizzard and winter storm watches for parts of Maryland, Washington, Virginia, West Virginia and Arkansas. The watches start as early as Thursday and stretch into Saturday.

“There’s a lot of details that are yet to be seen,” Otto said. “Subtle changes can make a big difference. We’ve seen that in storms in the past.”

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AIR TRAVEL

All major airlines have issued waivers for travel over the weekend, allowing passengers to rebook onto earlier or later flights to avoid the storms. The airports included vary by airline but include some cities in Kentucky, Tennessee and West Virginia all the way up the coast to New Hampshire and Massachusetts.

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THE FIRST FLAKES

Snow in much of Kentucky and Tennessee led school districts and some universities to cancel classes Wednesday and contributed to at least one traffic death, and officials warned motorists to be cautious of slick roads.

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GUARD READY IN WEST VIRGINIA

West Virginia Gov. Earl Ray Tomblin mobilized the West Virginia National Guard to assist in the upcoming storm. The National Weather Service says some areas of the state could get up to 2 feet of snow.

PennDOT mechanics were busy making sure trucks were cleaned and in good repair so all equipment is ready to go whenever the snow starts falling, spokesman Gene Blaum said.

“We’ve used virtually no salt,” so far this season, he said. “But winter isn’t over.”

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MIXED IMPACT IN NEW ENGLAND

The storm’s impact on southern New England remained uncertain Wednesday, but officials were preparing for the worst.

The National Weather Service said there’s a potential for 6 inches of snow or more in the region. High winds and coastal flooding are possible.

The storm is expected to miss northern New England. Meteorologist Tom Hawley of the National Weather Service in Gray, Maine, says its path could shift but right now “all indications are that it will not amount to much” in the region.

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ANTI-ABORTION MARCH STILL ON

Organizers of the March for Life say their annual anti-abortion rally in Washington will be held Friday, as scheduled.

The rally on the anniversary of the Supreme Court’s Roe v. Wade decision is one of the largest events on the National Mall. Thousands of abortion opponents gather to listen to speeches before marching to the Supreme Court.

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STOCKING UP

While the snow fell, some people made their way to the grocery store to stock up on needed items.

In Louisville, Kentucky, Adrian Gardner packed gallons of milk, laundry detergent and bags of groceries into his SUV. None of it was for him.

“It’s for my momma,” he said. “I don’t want her to have to come out in this.”

Cary Prince of McLean, Virginia, picked up rock salt at the hardware store, but struck out on snow blower fuel, which was sold out. Still, she was stocked up on the key provision, so all was well.

“I’ve got my wine,” she said.

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Associated Press writers Jessica Gresko in Washington, Kristen de Groot in Philadelphia and John Raby in Charleston, West Virginia, and AP Airlines Writer Scott Mayerowitz and AP Airlines Writer Scott Mayerowitz in New York contributed to this story.